Fundamentals in Focus: Rubner's Case for Selective Conviction

After months defined by macro headlines, positioning resets, and shifting AI narratives, the catalyst calendar has rotated back to earnings. In his October Update: Fundamentals in Focus¹, Citadel Securities' Scott Rubner lays out a constructive but selective case for U.S. equities into Q4, anchoring it in four interlocking themes: an earnings season that continues to outrun expectations, early signs of broadening participation, a retail investor returning with fresh conviction, and a volatility regime that rewards single-stock positioning over index exposure.

1. The Earnings Bar Keeps Moving Higher

Consensus entered Q3 reporting looking for approximately 27% year-over-year S&P 500 EPS growth — the third-highest expectation heading into any earnings season on record. The bar has not come down. Rubner notes that "earnings expectations have continued to move higher despite the recent weakness in equities," and that over the past four quarters, S&P 500 companies have raised guidance nearly three times for every cut — "the most supportive stretch of corporate guidance in 20 years of data."

The calendar ahead is unusually concentrated. Roughly 47% of S&P 500 index weight and one-third of expected earnings growth will report in the next two weeks. Growth itself is narrow at the top: MU and NVDA alone account for 36% of expected S&P 500 earnings growth, and the ten largest contributors represent roughly two-thirds of the total. Excluding those ten companies, expected growth falls to approximately 11%. And yet roughly 74% of S&P 500 companies are expected to deliver positive year-over-year earnings growth.

The divergence between rising estimates and falling valuations is particularly pronounced in AI-exposed sectors. Since June 30: Memory forward EPS estimates are up 25% while the forward P/E has fallen 34%; AI Infrastructure forward EPS is up 25% while the forward P/E has fallen 22%; the S&P 500 overall has seen forward EPS rise 10% against a 6% decline in the forward P/E.

The corporate bid adds another layer. U.S. companies have announced a record $1.3 trillion of share repurchase authorizations year-to-date. With 76% of the S&P 500 currently inside buyback blackout windows, Rubner observes that "the corporate bid is approaching an important turning point" as those windows lift through October and November.

2. Early Signs of Rotation

The S&P 500 Equal Weight / Nasdaq 100 ratio reached its lowest level since April 2000 on October 7. Since that trough, equal weight has outperformed the Nasdaq 100 by 2.8%, with 76% of S&P 500 constituents outperforming over the same window. Market breadth has also improved: the share of S&P 500 names trading above their 50-day moving average has moved from 25% to 37% since Rubner's last note.

"The reversal is still early, but notable."

Rubner is measured about what this means. Historically, fewer than half of similar rebounds from extreme relative-performance lows have led to sustained rotations. The move is worth watching, not extrapolating.

3. Retail Returns with Conviction

Last week, retail investors net bought $9.1 billion of U.S. equities on Citadel Securities' platform — the largest weekly net buy in over a year. Rubner notes the increase "has been driven by stronger directional conviction rather than elevated volumes." This is deliberate positioning, not noise.

The concentration of that buying underscores the thesis: Semiconductors attracted $2.6 billion in net purchases (96th percentile over the past year); AI Infrastructure added $2.4 billion (94th percentile); Neocloud names saw $700 million of net buying, the largest weekly accumulation Rubner's team has observed in that group. In fixed income, retail net bought nearly $3 billion across bond ETFs in the first seven sessions of October alone — a record pace of demand.

4. Still No Bid for Index Volatility

The spread between average S&P 500 constituent implied volatility and S&P 500 index implied volatility has widened by nearly 4 vol points to 24.7, now sitting in the 90th percentile of history. The absence of correlated selling explains it. The S&P 500 has not experienced a 2% move in either direction since June 5 — a stretch of 88 trading sessions. Just three 1% moves have occurred in the 41 sessions since the August 13 high, versus nine in a typical window. The market is approaching a full year without a single 80% NYSE downside-volume day; since 1996, the average year has seen 21 such sessions.

"Despite macro uncertainty, geopolitical headlines, and some extreme moves across individual sectors and names, we have not seen the broad-based selling that would push index volatility higher."

Index implied volatility near one-year lows offers relatively attractive entry points for hedges, while single-stock volatility — with earnings as an added catalyst — has further room to run. Rubner continues to favor "selective single-stock exposure over simply adding index beta."

5 Key Takeaways for Advisors and Investors

1. Earnings remain the anchor. Forward EPS estimates continue to rise even as multiples compress. The guidance cycle is the most positive in 20 years of data. The fundamental case for equities is intact.
2. Concentration risk cuts both ways. MU and NVDA alone account for 36% of expected S&P 500 earnings growth. Broad index exposure is an implicit bet on a narrow set of names; selective single-stock positioning is the more appropriate response.
3. The rotation is worth monitoring, not trusting yet. Equal-weight recovery from April 2000-level lows is historically rare. Early breadth improvement is encouraging, but fewer than half of similar episodes have led to sustained rotation.
4. Retail conviction is back — and directional. Record-paced retail buying in semiconductors, AI Infrastructure, and fixed-income ETFs signals genuine re-engagement. The move is concentrated in themes with fundamental earnings support.
5. The volatility regime favors single-stock hedging. With index implied volatility near one-year lows and the spread to single-stock volatility at the 90th percentile of history, earnings season creates an asymmetric opportunity: index protection is cheap while idiosyncratic risk premium is elevated.

Footnote:

1 Rubner, Scott. "October Update: Fundamentals in Focus." Global Market Intelligence, Citadel Securities, 14 Oct. 2026, https://www.citadelsecurities.com/news-and-insights/global-market-intelligence/october-update/.